1. Field of the Invention
The present invention relates to a device in a matrix printing head with at least one printing needle, one electromagnet, which is provided with an armature co-operating with the needle for moving the latter towards a printing position, and spring means for returning the needle in a direction from the printing position.
2. Description of the Prior Art
A plurality of devices described above are known in the art. In most devices each printing needle is fixed to a pivotable armature which pivots in an arcuate path each time the electromagnet is energized and de-energized, respectively. Depending on the rigid connection between the armature and the needle the connection, the needle and/or the armature are subjected to stresses, which will wear and/or damage these elements and even break them. Moreover, the rigid connection has made impossible an exchange of the armature only or the needle only in the case one of these elements has been broken and has made more difficult the mounting of the elements in the printing head.
In order to solve the two problems described above it has been proposed in Swedish Pat. No. 76 06230-6 to detachably connect the armature to the printing needle. This means that the needle or the armature can be exchanged and the mounting of these elements can be made easier. However, the detachable connection between the armature and the needle acts as a rigid connection during the work of the printing head because no movement between the armature and the needle is possible. The change of the angle between these elements during the pivoting movement of the armature is accomplished by bending the needle near the armature. This bending relatively quickly fatigues the printing needle so that it will be broken.